1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to generation and application of a sequence for a reference signal in a wireless communication system.
2. Related Art
Wireless communication systems are widely spread all over the world to provide various types of communication services such as voice or data. In general, the wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of the multiple access system include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, etc.
In the wireless communication system, a sequence is generally used in various usages such as a reference signal, a scrambling code, etc. The sequence used in the wireless communication system generally satisfies the following properties.
(1) A good correlation property for providing high detection performance.
(2) A low peak-to-average power ratio (PAPR) for increasing efficiency of a power amplifier.
(3) Generation of a large number of sequences to transmit a large amount of information or to facilitate cell planning.
Although a constant amplitude and zero auto correlation (CAZAC) sequence having a good PAPR property has been proposed, the number of available sequences is limited. Therefore, many wireless communication systems use a sequence generated in a pseudo-random manner. A pseudo-random sequence has an advantage in that a large number of sequences are available, but has a problem of a high PAPR in a specific pattern.
Various binary or non-binary pseudo-random sequences have been used in the wireless communication system. The pseudo-random sequences can be easily generated using an m-stage linear feedback shift register (LFSR), and have a significantly excellent random property. An m-sequence is used as a scrambling code in a wideband CDMA (WCDMA) system since a structure of the m-sequence is simpler than the non-binary pseudo-random sequence.
A gold sequence is a pseudo-random sequence generated by using two different binary m-sequences. The gold sequence can be easily implemented by two m-stage LFSRs. The gold sequence has an advantage in that different pseudo-random sequences can be generated in accordance with a period while varying an initial state of each m-stage LFSR.
Accordingly, there is a need for a method capable of generating a sequence with improved PAPR and correlation properties.